Stitch Type

SPI (Stitches per inch) – What you should know When setting standards for stitches per inch, you should always keep in mind that more stitches per inch required in a seam, the longer the sewing cycles to complete the seam. Longer sewing cycles translates into higher labor costs and lower production levels. A sewing machine sewing at 5,000 SPM (stitches per minute) at 8 SPI will sew 17.4 yards of seam per minute. A sewing machine sewing at 5,000 SPM at 14 SPI will sew 9.9 yards of seam per minute.

More stitches per inch will also consume more thread per inch of seam. This will contribute to higher seam strength and more elastic seams, but will also increase the consumption of thread required to sew the garment.

Therefore, the recommendations listed above are common stitch levels that provide adequate seam strength but also take into consideration the factors just mentioned. When sewing knit fabrics, you should always check for excessive “seam grinning” of the seam and also check for “stitch cracking”. “Seam grinning” occurs when thread stitch balance is too loose allowing the seam to open up too much when stress is applied to it. “Stitch Cracking” is checked by applying pressure on the seam in the stitching direction. If the thread tensions are too tight or if you are not using enough stitches per inch, the threads will rupture as stress is applied on the seam. Therefore, the following recommendations have been made for the number of stitches per inch to be used on the following garments.

KNIT GARMENTS

Garments

SPI

Comments

Garments

SPI

Comments

Jersey T-shirts, Tops, Polos

10-12

Using more SPI increases the chance of needle cutting.

Swimwear

12-16

The more elastic the seam, the more SPI that should be used to minimize stitch cracking. The more elastic the seam, the more SPI that should be used to minimize stitch cracking. The more elastic the seam, the more SPI that should be used to minimize stitch cracking.

Underwear

12-14

The more elastic the seam, the more SPI that should be used to minimize stitch cracking. The more elastic the seam, the more SPI that should be used to minimize stitch cracking.

Dresses, Skirts

10-12

Infant Wear

10-12

Intimates

12-16

Knit Garments continued on next page.